1. Field of the Invention
The present invention relates generally to a disk drive apparatus for rotating a disk, such as a floppy disk, a microfloppy disk and so forth. More specifically, the invention relates to a chucking mechanism for a disk drive, which can accurately position or center the disk.
2. Description of the Prior Art
As is well known, magnetic disks, such as floppy disks, microfloppy disks and so forth, most commonly have a center aperture and a drive aperture offset from the center aperture. Generally, such a disk drive is provided with a center positioning pin engageable with the center aperture of the disk, and a drive pin which is engagable with the drive aperture of the disk. The center positioning pin and the drive pin project from a turntable which is driven to rotate by means of a known drive mechanism.
This type of magnetic disk and the disk drive apparatus adapted therefor is disclosed in U.S. Pat. No. 4,445,155, to Takahashi et al, on Apr. 24, 1984, which is assigned to the owner of the present invention. Disclosed in U.S. Pat. No. 4,445,155 is a flexible magnetic disk of typical microfloppy construction and a disk drive therefor.
The disclosed flexible magnetic disk cassette has a flexible disk enclosed in a cassette casing made of an upper half and a lower half. The lower half has a drive hole through which a center positioning pin of a disk drive apparatus may extend into the center aperture of a center core disk rigidly and non-removably secured at the center of the disk. The center core disk also has a driving and positioning means for receiving a drive pin of the disk drive apparatus. The driving and positioning means is structured so that engagement with the drive pin will cause the disk to move until the center aperture of the attached center core disk is in proper centering engagement with the positioning pin.
In order to drive the flexible magnetic disk as set forth above, the disk drive apparatus comprises a center positioning pin and a spring-biased drive pin provided on a rotational drive. The center positioning pin is inserted in the center aperture means. The spring-biased drive pin is inserted in the driving and positioning aperature means during operation. The spring-biased drive pin is spring-biased so as to permit tilting of the pin to effect an at least partial radial displacement of at least the top of the pin in a vicinity of the driving and positioning aperture means when engaged with the positioning aperture.
The prior-art disk drive apparatus discussed above encounters a drawback in that the rotational torque that can be applied to the disk is limited. In other words, when rotational torque in excess of a predetermined value is applied, the spring-biased drive pin can no longer be biased toward the peripheral edge of an opening constituting the driving and positioning means, i.e. the biasing force exerted on the drive pin will no longer be sufficient to establish firm contact between the peripheral edge of the opening and the drive pin. As a result, the disk cannot be accurately centered.
On the other hand, when driving a magnetic disk the highest possible rotational torque is considered to be desirable in order to reduce the need for highly accurate adjustment of the friction between the disk or a disk-lifting pad and a magnetic head of a recording and/or reproducing apparatus.